Rotary helical splined actuators have been employed to achieve high-torque output from a piston driven along a linear path. In typical arrangements, the actuator includes a cylindrical body with a rotary output shaft extending coaxially within the body, with an end portion of the shaft providing the drive output. An elongated angular piston sleeve has a sleeve portion splined to cooperate with corresponding splines on a ring gear attached to the side wall of the body, as well as with splines on an outer surface of the output shaft. The piston sleeve is reciprocally mounted within the body, such that pressurized fluid may be applied to opposing sides of the head to produce reciprocal axial movement of the piston sleeve.
As the piston sleeve linearly reciprocates in an axial direction within the body, the outer splines of the sleeve portion engage or mesh with the splines of the ring gear to cause rotation of the sleeve portion. The resulting linear and rotational movement of the sleeve portion is transmitted through the inner splines of the sleeve portion to the splines of the shaft to cause the shaft to rotate. Bearings rotatably support the shaft relative to the body.
Fluid-powered rotary actuators find wide application to move, support, and position rotary loads. Example industries in which rotary actuators are widely used include agriculture, construction, material handling, and mining. A common use for fluid-powered rotary actuators is in connection with a boom, wherein the actuator is employed to rotate an implement mounted to a distal end of the boom about the output shaft axis. Examples include aerial work platforms for platform, basket, and jib rotation, as well as construction equipment and agricultural harvesters for the positioning of boom attachments.
Certain boom attachments require the supply of pressurized fluid for operation, such as working implements. A particular example is tree-trimming apparatus, which includes a large diameter circular saw mounted at the distal end of the boom, and powered by a high speed hydraulic motor. Pressurized fluid supply lines must therefore extend between the pressurized fluid-powered motor and a pressurized fluid source. Pressurized fluid supply lines positioned along the boom exterior can become entangled among foreign objects at the worksite, and may also be at risk for damage through puncture or cutting. Such risks and drawbacks are exacerbated when the boom has a telescoping function, wherein the pressurized fluid tubing must be provided with sufficient/excess length to accommodate the adjustable extension of the boom.
It would therefore be desirable to supply working implements at the end of a boom with pressurized fluid lines that are protected from interference and damage. The pressurized fluid supply lines may be so protected within the interior of the boom, wherein a need exists to communicate pressurized fluid from within the interior of the boom to an operating implement, and particularly in circumstances wherein the operating implement is rotatably coupled to the boom with one or more rotary actuators.